4-aminobutyratepyruvate transaminase is a pyridoxal phosphate-dependent enzyme with systematic name 4-aminobutanoate:pyruvate aminotransferase. This enzyme is a type of GABA transaminase, which degrades the neurotransmitter GABA. It catalyses two chemical reactions. In the first, pyruvic acid is the amino group acceptor and the second product is L-alanine:
In the second reaction, glyoxylic acid is converted to glycine when succinic semialdehyde is formed:
In this case, the reaction is not reversible, unlike in the first example. The enzyme has been characterised from tobacco, Arabidopsis, and tomato.
Clinical significance Phenylethylidenehydrazine, an active metabolite of the drug phenelzine (brand name Nardil among others), inhibits gamma-aminobutyric acid transaminase and consequently increases GABA concentrations in the central nervous system. This may contribute to the notable anxiolytic effects of phenelzine.
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